1. Field of the Invention
The present invention generally relates to the use of safety handles that are placed about the periphery of heavy equipment to protect the operator's hands from injury. More particularly, the invention relates to safety handles that are mounted to the periphery of manual pipe tongs, which are typically used in the oilfield drilling industry. More particularly still, the invention relates to multi-piece, reinforced, and replaceable handles for manual pipe tongs that protect oilfield workers' hands from injury that might otherwise result from impact with adjacent equipment.
2. Description of the Related Art
Manual pipe tongs are used throughout the oilfield industry to apply torque to various tubular components of generally cylindrical shape. This application of torque is most often used to secure, tighten (make-up), and loosen (break-out) the threaded rotary connections of drill pipe, drilling collars, casing and tubing. Pipe tongs typically function by incorporating a cantilevered configuration that holds the workpiece in a grip that tightens or loosens depending on the direction that torque is applied to the lever arm.
FIG. 1 shows a typical prior art manual tong assembly 10 as used in oilfield drilling operations to secure or rotate a cylindrical workpiece 12. Manual tong assembly 10 includes a long jaw 14, a short jaw 16, a lug jaw 18, and a lever arm 20 all connected together at pivot points 22a, b, c, d. A latch 24 is pinned to one end of the long jaw 14 and fits into a receiver step 26 at the end of the lug jaw 18.
FIGS. 2a and 2b show how different workpiece 12 sizes can be accommodated by adjusting the lengths and configurations of lug jaw 18. FIG. 2a shows the lug jaw 18 of FIG. 1 that includes an array of mounting locations 28 and a choice of receiver steps, 26 and 30, that may be used to adjust the manual tong apparatus 10 to various diameters of workpiece 12 (e.g. pipe diameters). Alternatively, FIG. 2b details a lug jaw 32 that is longer in length and includes a hinged portion 34 attached to the lug portion 36 by means of a hinge pin 38 so as to allow even larger diameter workpieces to be accommodated by tong assembly 10.
Referring again to FIG. 1, jaws, 14, 16, and 18 are positioned in place around workpiece 12 and locked into place with latch 24. In some instances, each jaw may contain one or more sets of sharpened teeth called tong dies 40 that are used to "bite") into workpiece 12 and prevent slippage when manual tong 10 is engaged. Once latch 24 is engaged, lever arm 20 can be rotated in direction .alpha. so as to load latch 24 in tension and engage and apply torque to workpiece 12 in that direction. Rotating lever arm 20 in direction .omega. will loosen the grip of jaws (14, 16, and 18) on workpiece and allow latch 24 to be opened. Because tool 10 is quite large, with lever arm 20 typically being 3-6 feet long, operation usually requires more than one person. Several handles, such as 42 or 44, are typically placed about the periphery of manual tong assembly 10 to provide locations for rig workers to guide it when moving tong assembly 10 into position on the pipe, or to remove it from the pipe.
Manual tong 10, as illustrated, is configured to grip workpiece 12 only when torque is applied in the .alpha. direction. Typical rig operations incorporate two sets of manual tongs, with each being a mirror image of the other, so that one tightens in clockwise direction and the other in a counter-clockwise direction. Each can tighten or loosen the pipe threads, depending on whether it is installed in the upper position and engages the pin (male) connection or the lower position for engaging and holding the box (female) counter. Typical operations will include the use of two, opposed tongs. When more than one tong is used, their positions on the workpiece relative to each other depends on the operation being performed and the type of additional rig equipment used.
Operators typically position and manipulate manual tongs 10 by grabbing handles that are provided about the periphery of the tongs as, for example, handles 42 and 44 in FIG. 1. FIGS. 3a, 3b, and 3c show three different designs of tong handles that have been previously known and used on manual tong assemblies. FIG. 3a shows a manual tong apparatus that includes a handle 50 made from U-shaped a cylindrical rod that has been cast or welded onto the body 52 of the tong. To manufacture handle 50, the cylindrical rod is bent into top, middle, and bottom sections 54, 56, 58, respectively. Although this design is the simplest and most cost effective for a manual tong manipulator handle, it offers the least protection to the operator, as a hand wrapped around handle 50 is exposed to blows from above, below, or horizontally.
In order to gain maximum protection from injury while using tongs with a handle of this design, the operator must fight his natural tendency to place his hands on top 54 and bottom 58 portions and must grip only middle portion 56 of handle 50. This is because serious injury can result to an operator's hands when he is manipulating one set of tongs around the pipe while another set of tongs is being manipulated around the pipe, either above or below his tongs. If an operator's hand is exposed while two sets of adjacent tongs move relative to each other, it can be pinched or crushed between the tongs. The design of FIG. 3a offers little protection from injuries of this type, as the operator is comfortably able to grip the handle in any number of unsafe ways.
FIG. 3b demonstrates a handle system 60 that is designed to prevent the type of hand injuries experienced while using the design of FIG. 3a. Handle 60 includes a tong body 62 with a rod-style handle 64 as before, but with the addition of metal guard plates positioned in a horizontal plane of each end of vertical handle 64. Metal guard plates 66 and 68 are intended to both restrict placement of hands to the center section of handle 64 and to protect the operator's hands from being crushed or impaled by an adjacent tong or other nearby equipment. Metal plates 66 and 68 can be either cast or welded into place as original equipment when the tong body 62 is manufactured or can be retrofitted to existing tongs as a safety upgrade. While the addition of metal plates 66, 68 is an improvement to the handle assembly 50 of FIG. 3a, they do not offer any shock absorbing characteristics. If an operator were to have a hand resting upon metal plates 66, 68 and that hand were to be impacted by another object, it is possible that the operator's hand or fingers could become crushed or severed. To ensure that tong handle devices pose as little safety risk as possible, it is best that they be manufactured or retrofitted with shock absorbent devices.
FIG. 3c shows another embodiment for a tong handle, which utilizes a one-piece polyurethane dumbbell-shaped design to address the shock absorbency concerns of handle 60 of FIG. 3b. Polyurethane dumbbell 70 is attached to tong body 72 by cutting out middle portion 56 in FIG. 3a and utilizing horizontal portions 54 and 58 (74 and 76 in FIG. 3c). One-piece dumbbell 70 includes a generally cylindrical handle section 78 with disc shaped flange portions 80, 82 above and below handle section 78. Holes are drilled for spring pins in the ends of horizontal members 74 and 76, and one-piece dumbbell 70 is fitted onto horizontal members 74 and 76. Separate spring pins, 84, 86 are driven through opposite ends of dumbbell handle 70, to engage horizontal members 74 and 76 and hold dumbell 70 in place on tong body 72. Flanged portions 80 are preferably larger in diameter than an operator's fist so that they are able to act as large bumpers to protect operator's hands from damage.
Dumbbell 70 is manufactured of a shock absorbing material. When operator uses dumbbell handles 70 to manipulate manual pipe tongs, his hands are protected from impact and scrapes with other equipment as long as his hands are positioned on cylindrical handle section 78. Unfortunately, the dumbbell design of FIG. 3c has drawbacks that can reduce its effectiveness, preventing many drilling contractors from adopting it.
One-piece dumbbell 70 is sometimes installed as a retrofit on tongs with existing handles as shown in FIG. 3a. The vertical distance between existing horizontal members 74 and 76 in FIG. 3c is typically different for various handle locations on the same tong, and of course, on different tong models. Due to the need for economical production of a one-piece molded dumbbell handle 70, one size of one-piece dumbbell handle 70 is utilized in as many different locations as possible. This results in some compromises in fitting, such that one-piece dumbbell handle 70 is sometimes installed in a slightly bent or compressed or stretched or loose condition, which may contribute to a premature failure of this part.
Because the material of dumbbell 70 must be somewhat soft in order to have good shock absorbing properties, it is also somewhat flexible. The flexibility of handle portion 78 can cause it to break and tear away prematurely. In the event of a failure of handle portion 78, dumbbell 70 is unusable and must be replaced before the tong 72 can be safely operated again. If a replacement is not immediately available, since minimal amounts of replacement parts are typically carried on the work location, a drilling rig crew might be tempted to manipulate the manual tong apparatus outside the designated handle area 78, such as by grasping 74 and manipulating tong 72 with hands outside the protected area between 74 and 76. This temptation to use the crippled tong assembly in an unsafe manner, while parts are on order, results in greatly increased risks to the health and safety of the operator.
Because of the increased potential for injury in the event of a failure of this design, drilling operators may be reluctant to deploy dumbbell handles 70 with their manual tong assemblies, thus not taking advantage of any safety improvements that that may otherwise be realized. Hence, it is desirable to provide an effective manual tong handle that is safer, more reliable, and reduces the risk of injury.